A systematic study on the automerization barrier of singlet propynylidene has been carried out. The effect of the basis set dependence and the inclusion of the triples excitation on both the geometries and energies of the C-2v and C-s isomers has been considered. An estimation of the basis set limit has been done, which confirms previous work in the sense that the automerization barrier is below 1 kcal/mol with the C-s isomer being the most stable one.